 The U.S. House of Representatives' 435 members are elected to two-year terms, with elections held in the fall of every even-numbered year (i.e. 2000, 2002, 2004). Each member represents a single district drawn by each state. Due to redistricting, which takes place every 10 years, some races may include two incumbents.
 How does CNN call projected winners in races? Click here.